Total depth after etching is 11.756 um
Calculated remaining resist as 7.37um, indicating an erosion of 1.38um in 10 minutes of etching
This equates to an erosion rate of 138 nm/min
The etch depth of 4.39um in 10 mins indicates an etch rate of 439.0nm/min
The selectivity is therefore 3.19:1